The present invention relates to casters in general, and more particularly to improvements in blocking devices which serve to oppose rotation of the wheel and/or swiveling of the wheel frame in a caster for use on vehicles, pieces of furniture, appliances and the like.
It is already known to install a portion of the blocking device for the wheel and wheel frame of a caster in a cavity or chamber between the frame and a carrier which supports the frame and to which the frame is connected for swiveling movement about the axis of a thrust bearing. In accordance with a presently known proposal, the web of the bifurcated wheel frame is rigidly connected with a turntable which can swivel relative to the carrier between an upper and a lower annulus of antifriction rolling elements. A braking lever is installed in the wheel frame at a level below the web and is movable into frictional engagement with the peripheral surface of the wheel by a bolt which extends through the carrier, through the turntable and through the web of the wheel frame. The bolt is reciprocable in a sleeve which is surrounded by a plate-like blocking member. The blocking member is movable in the axial direction of but cannot rotate relative to the sleeve and is non-rotatably connected with the bolt in such a way that it can yield by moving upwardly under the action of a spring. The periphery of the blocking plate is formed with an annulus of gear teeth which can mate with an annulus of internal teeth in the platform to thus hold the wheel frame against swiveling movement with reference to the carrier. The plane in which the blocking plate is held against rotation relative to the bolt coincides with the plane in which the blocking plate is held against angular movement with reference to the sleeve. This entails unavoidable weakening of the blocking plate which is particularly undesirable if the blocking plate and other parts of the blocking device are made of relatively inexpensive materials in order to reduce the overall cost of the caster. It has been found that, when using relatively soft synthetic plastic materials, the component parts of the blocking device tend to undergo extensive deformation which is likely to prevent the device from properly opposing or preventing swiveling movements of the wheel frame with reference to its carrier.